Rocks Hidden Beneath the Pacific May Hold a Secret Record of Earth Slowly Cooling

Deep, deep down in the Pacific Ocean, there is an enormous underwater plateau called the Shatsky Rise, which is considered to be a geological feature that holds the key to the changes that have been happening in the Earth's interior over the years.

Recently, geoscientists have been interested in certain abnormal sedimentary rocks, called cherts, which can be found in this area, and they have been instrumental in helping geoscientists learn about the thermal history of the ancient ocean floor, which was formed during the Cretaceous period.

As explained by Phys.org, geoscientists have been able to learn that oxygen isotopes that can be found in these sedimentary rocks can be used to learn about the amount of heat that once passed through the Earth's crust, as explained by Phys.org.


These isotopes, which can be considered as tiny thermometers, have been able to allow geoscientists to learn about geological events that happened tens of millions of years ago.

How Chert Rocks Preserve Heat History

The chert is composed of silica, which is rich in sedimentary rock. This type of sedimentary rock is formed deep in the ocean as microscopic marine life drops silica that accumulates on the ocean floor. In the process, oxygen isotopes are locked into the mineral structure of the sedimentary rock, which change in relation to the temperature and heat flow of the crust.

Scientists analyzing cherts from the Shatsky Rise have been able to determine that the isotopes in the sedimentary rock accurately correlate with the amount of heat that was moving through the ocean crust as the sedimentary rock was formed. As explained in research presented by EurekAlert, isotopes in sedimentary rock can be used as an accurate method of determining geothermal gradients, which are the temperature differences that exist in the Earth's crust.

Evidence of a Cooling Planet

The new analysis supports the broader scientific understanding that Earth has been cooling over time since its creation billions of years ago. This is because the heat generated at the early stages of the Earth’s development and the subsequent decay of radioactivity within the Earth’s mantle eventually works its way through the crust and into space.

The examination of the samples of chert gathered from the Shatsky Rise enabled the scientific team to obtain evidence of the reduction of heat flow over aged oceanic crust, which confirms long-standing scientific theory. The study published through Phys.org explains that the new research provides one of the most direct records of how the ocean floor cooled over time, particularly within the Cretaceous period, which spanned 66 million to 145 million years ago.

Earth’s internal heat changes can also have an effect on surface features and long term climate patterns. It is believed that changes in heat flow can affect volcanic eruptions, which in turn can emit huge amounts of greenhouse gases into the atmosphere.

Research into past geological occurrences, including the Cenomanian Turonian boundary event, has revealed that periods of high volcanic activity and ocean chemistry changes have been associated with major environmental changes in Earth’s history.

Confirming the Method Through Global Research

In order for their results to be accurate, scientists compared their isotope results from Shatsky Rise with other results obtained from independent measurements conducted by international ocean drilling operations. These operations offer detailed records from various areas on the seafloor.

EurekAlert reported that the results obtained by the researchers had strong agreement with previously known patterns of heat flow in the oceanic crust. This, therefore, validated the results obtained by confirming their reliability. This is important since this confirms that chert rocks could be reliable indicators of geothermal conditions.

The success of this method provides an opportunity for further research into the thermal evolution of our planet and geological activities. It is believed that if scientists study the chert formations in other parts of the ocean, they might fill in some of the gaps in our knowledge about the flow of heat within our planet.

A study published by Phys.org indicates that if we improve our knowledge about the flow of heat within our planet, it might be very beneficial for our understanding of geothermal energy potential and natural resources.